When I can't write, I can get a bit reckless and do things that I wouldn't normally do. My whole life sort of goes out of balance. So to help avoid that I have a friend who will sit down and talk about story stuff with me. She'll also give me writing prompts that aren't directly related to the story in order to help me find some inspiration. It doesn't always help, but it can sometimes. Other than that, I'll read a lot. Usually something sparks and I can get back to writing.

I watch anime. No seriously, that's what I do.
They'd usually come when I'm watching an anime, cooking food, or even taking a shower. That's why unless you have good memory, it's helpful to carry around a small notebook to jot ideas down because you honestly will never know when that "AHA!" moment will come.

Yea I also do something else . Like read! I get lots of ideas from books and anime and I somehow manage to combine them to make ONE story.
~AzunOrAzucena

When I've been stuck mid-novel I like to write a couple hundred words of nonsense, creating a short story of tomfoolery that can be thrown away afterwards. I once wrote the tale of a dust mote drifting through a vent, envious of the pollen molecules floating alongside... The stupider the better....Ridiculous, but gets the creative juices flowing again and lets you approach your book with a fresh perspective.

My experience with writer's block has usually been that I will reach a fork in the logically viable plot line whose branches aren't easy to choose between, and so I will keep arguing with myself over which set of constraints I want to establish for myself and my characters. I'm typically better able to choose after separating myself from the project for a short while. The effect is even stronger if I actually leave the room I've been writing in entirely during this break, and breaks might range from half an hour to a few days.

I think the best thing you can do is move your body when your stuck. Brain chemistry suggests that when the body is in motion, the brain reacts quicker, is more at ease, and it has an easier time coming up with new ideas. That's why in businesses now "walking meetings" are becoming a trend.

My inspiration tends to show up at the oddest times, so I will tend to write a brief 1-3 line summery of what the idea is and let it 'cook'. This helps get me work around writers block sometimes because I'll have several things I can work with already waiting. Usually though, so long as I can get things moving, the momentum will help break through. Even if the results aren't as high of a level as I would usually get, I can go back later and touch things up.

In a different aspect, where I am specifically sitting down to write, occasionally for some reason feel either a heavy lack of enthusiasm or restless. In those instances I usually have to dispel those first. Restlessness is usually fixed by a walk to move some of that energy to my mind, but lack of enthusiasm sometimes takes resorting to changing my emotional energy. It's a technique I worked out in the past to take the current specific emotional energy and turn it into raw energy before I bring it back as a different type. Anger to optimism for example. Likely from too many years of solitary introspection.

What I would usually do is take a shower. For some odd reason, I just think more clearly when I am taking one. For you, it greatly depends on what has you stuck. I'd recommend going back to what originally inspired you or something that has helped you before with your writing. Pick up a poem, a story, or a book that is related or completely different from what you are writing. Inspiration can come from anywhere. Let your mind just think about it, don't force yourself to just think of an idea that you'd need now. Let all of the stupid ones in and think about how to make those better so you could use them.

Those are just ideas that I have. I am not sure if any of them will help you. Where people get inspiration from varies far and in-between. You just have to find what inspires you and go from there.

I keep going as if I never intended to write in the first place. I travel on for up to several years looking at my feet and berating myself for having nothing to write about.

Then I get bored, go out and do something, anything, where I'm forced to be around people. After my panic attack is over, I slowly start to remember what happened in the calmer moments, when I wasn't totally blackout anxious. Then the rest comes back at a manageable pace, as if I was reading it. And after that, if I'm not too rusty, I can put my voice into the words on the page and say everything that got stuck in my chest.

Then I can use all these pieces any time I'm writing a story and I don't know where a character should go, what they should say, how they should act. The problem is, writing a complete fictional story takes some extra imagination that I'm not sure I've always got. So I'm stuck with pieces, I can only conclude my method is not as good as O. Henry's. I believe that guy could really lay the pieces as he went.

Lately an insurmountable writer's block of mine was shattered by a short relationship. Not the shortest I've had, but strangely it was the most honest. I think she cracked under the pressure of her own self-scrutiny. But after that mess, where we dumped heavy issues in a pile together and tried to walk forward like nobody had to carry them anymore, she decided I was too quiet or serious or nice. Or maybe she thought I was dumb, uncommitted, too reliant on a plan. And where it used to hurt before, it was less painful, more of just something to observe, feel, and find a way to put into words.

Either way, the main keys I've found to being a good writer are patience, honesty, and dissatisfaction. But to warn you, these are also the main keys to being an alcoholic.

My housemate has just told me it's the twist that matters. So, for his sake I will tell you just come up with a twist when you don't know what else to write (I disagree, the twist should only happen when the writer is certain of a truth that includes the twist, then it's just timing when the reader will be certain.)